Torque impact mitigator for power tong

ABSTRACT

A torque impact mitigator including a housing assembly having a hydraulic cylinder. A piston is disposed within the hydraulic cylinder. A piston rod is mounted at a first end to the piston and having a second end extending out from the compression end. A compression spring is disposed between the piston and an end of the hydraulic cylinder. A rod clevis is secured to the second end of the piston rod. A plug is disposed within an upper end of the compression spring and having a bore extending therethrough to receive the piston rod. One or more bores are disposed through the piston to allow passage of hydraulic fluid into the hydraulic cylinder. A damper tube connecting the compression end and the rebound end of the hydraulic cylinder to direct the hydraulic fluid therethrough to further control the speed of the piston.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation-In-Part application of U.S.application Ser. No. 16/208,760 filed Dec. 21, 2018.

BACKGROUND OF INVENTION

In the drilling and completion phases in exploring for oil and gas, pipetongs have been utilized for engaging lengths of casing, drill orcompletion pipe, known generally as tubular members, end to end, by rigfloor personnel operating power tongs directly and in close proximity tothe tubulars on the rig floor. A typical casing power tong comprises aset of jaws to make up or break up the joint. The power tongs may weigha few thousand pounds and are usually supported from the rig by a cablethat allows the power tong to be moved manually by the rig floorpersonnel to engage the pipe, or disengage from the pipe, and bepositioned away from the pipe string, to allow other work to proceed.The power tong is connected on the one end to the rig cable.

However, because of the size of the power tongs, more than a singleindividual, often times two or three men, are required to move the tonginto position, and operate the tong to make up or break the joint, andthen to manually swing the tong, hanging from the cable, out of the way,and engage it in a position away from the pipe, so that the rigpersonnel can proceed to other chores. This manual operation of the tongin and out of position must be done with care, since the tong, swingingfree from the cable, may strike one of the workers, or inadvertentlydisengage from its position and injure workers or damage materials onthe rig floor.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, there is discloseda torque impact mitigator. The torque impact mitigator includes ahousing assembly including a hydraulic cylinder having a compression endand a rebound end. A piston is disposed within the hydraulic cylinder soas to reciprocate back and forth. A piston rod is disposed within thehydraulic cylinder and mounted at a first end to the piston and having asecond end extending out from the compression end. A compression springis disposed between the piston and the compression end of the hydrauliccylinder. A rod clevis is secured to the second end of the piston rod tocompress the compression spring into a compressed state when the rodclevis is moved away from the hydraulic cylinder and to release thecompression spring into a relaxed state when the rod clevis is movedtowards the hydraulic cylinder. A plug is disposed within an upper endof the compression spring and having a bore extending therethrough toreceive the piston rod. One or more bores is disposed through the pistonto allow the passage of hydraulic fluid into the compression end of thehydraulic cylinder when the compression spring is in the compressedstate, and to allow the passage of hydraulic fluid into the rebound endof the hydraulic cylinder when the compression spring is in the relaxedstate. A damper tube connecting the compression end and the rebound endof the hydraulic cylinder to direct the hydraulic fluid therethrough tofurther control the speed of the piston.

Further according to an embodiment of the present invention, there isdisclosed a torque impact mitigator to be used in conjunction with apower tong on an oil drilling rig. The torque impact mitigator isanchored to the drilling rig, whereby a cable is connected at one end toone end of the torque impact mitigator, and on an opposite second end tothe power tong. A second end of the torque impact mitigator is bemounted to a support on the oil well rig. A housing assembly includes ahydraulic cylinder having a compression end and a rebound end. A pistonis disposed within the hydraulic cylinder so as to reciprocate back andforth. A piston rod is disposed within the hydraulic cylinder andmounted at a first end to the piston and having a second end extendingout from the compression end. A compression spring is disposed betweenthe piston and the compression end of the hydraulic cylinder. A rodclevis is secured to the second end of the piston rod to compress thecompression spring into a compressed state when the rod clevis is movedaway from the hydraulic cylinder and to release the compression springinto a relaxed state when the rod clevis is moved towards the hydrauliccylinder. A plug is disposed within an upper end of the compressionspring and having a bore extending therethrough to receive the pistonrod. One or more bores are disposed through the piston to allow thepassage of hydraulic fluid into the compression end of the hydrauliccylinder when the compression spring is in the compressed state, and toallow the passage of hydraulic fluid into the rebound end of thehydraulic cylinder when the compression spring is in the relaxed state.A damper tube connecting the compression end and the rebound end of thehydraulic cylinder to direct the hydraulic fluid therethrough to furthercontrol the speed of the piston.

According to another embodiment of the present invention, there isdisclosed a method of using a torque impact mitigator in conjunctionwith a power tong on an oil drilling rig. The method includes anchoringthe torque impact mitigator to the drilling rig with a cable connectedat one end a first end of the torque impact mitigator and on an oppositesecond end to the power tong. Then, mounting a second end of the torqueimpact mitigator to a support on the oil well rig. Constructing thetorque impact mitigator from a housing assembly including a hydrauliccylinder with a compression end and a rebound end. Disposing a pistonwithin the hydraulic cylinder so as to reciprocate back and forth.Mounting a piston rod at a first end to the piston and extending asecond end of the piston rod out from the compression end of thehydraulic cylinder. Compressing the compression spring between thepiston and the compression end of the hydraulic cylinder into acompressed state when the piston is moved away from the compression endof the hydraulic cylinder and releasing the compression spring into arelaxed state when the piston is moved towards the rebound end of thehydraulic cylinder. Reducing the buckling of the compression spring fromas the spring is compressed with a plug having a bore extendingtherethrough disposed within an upper end of the compression spring.Finally, causing the passage of hydraulic fluid through one or morebores in the piston into the compression end of the hydraulic cylinderwhen the compression spring is in the compressed state and causing thepassage of hydraulic fluid through the one or more bores in the pistoninto the rebound end of the hydraulic cylinder when the compressionspring is in the relaxed state. Further controlling the speed of thepiston by directing hydraulic fluid through a damper tube having anadjustable flow control valve and interconnecting the compression endand the rebound end of the hydraulic cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS

The structure, operation, and advantages of the present invention willbecome further apparent upon consideration of the following descriptiontaken in conjunction with the accompanying figures (Figures). Thefigures are intended to be illustrative, not limiting.

Certain elements in some of the figures may be omitted, or illustratednot-to-scale, for illustrative clarity. The cross-sectional views may bein the form of slices, or near-sighted cross-sectional views, omittingcertain background lines which would otherwise be visible in a truecross-sectional view, for illustrative clarity.

Often, similar elements may be referred to by similar numbers in variousfigures (Figures) of the drawing, in which case typically the last twosignificant digits may be the same, the most significant digit being thenumber of the drawing figure (Figure).

FIG. 1 is a front, three-dimensional view of a torque impact mitigatorin use with a power tong, according to the present invention.

FIG. 2 is a front, three-dimensional view of a torque impact mitigator,according to the present invention.

FIG. 3 is a front, three-dimensional exploded view of the torque impactmitigator, according to the present invention.

FIG. 4 is a front, three-dimensional view of a spring disposed about apiston rod mounted to a piston, according to the present invention.

FIG. 5 is a side, cross-sectional view of the torque impact mitigator ina contracted condition, according to the present invention.

FIG. 6 is a side, cross-sectional view of the torque impact mitigator inan expanded condition, according to the present invention.

FIG. 6A is a side three-dimensional view of the piston, the piston seal,and the piston ring, according to the present invention.

FIG. 7 is a front, three-dimensional view of a torque impact mitigatorincorporating a damper tube including an adjustable flow control valve,according to the present invention.

FIG. 8 is a side, cross-sectional view of the torque impact mitigator ofFIG. 7 incorporating a damper tube including an adjustable flow controlvalve in an expanded condition, according to the present invention.

FIG. 9 is a side, cross-sectional view of the torque impact mitigatorincorporating a damper tube including an adjustable flow control valvein a contracted condition, according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the description that follows, numerous details are set forth in orderto provide a thorough understanding of the present invention. It will beappreciated by those skilled in the art that variations of thesespecific details are possible while still achieving the results of thepresent invention. Well-known processing steps are generally notdescribed in detail in order to avoid unnecessarily obfuscating thedescription of the present invention.

In the description that follows, exemplary dimensions may be presentedfor an illustrative embodiment of the invention. The dimensions shouldnot be interpreted as limiting. They are included to provide a sense ofproportion. Generally speaking, it is the relationship between variouselements, where they are located, their contrasting compositions, andsometimes their relative sizes that is of significance.

In the drawings accompanying the description that follows, often bothreference numerals and legends (labels, text descriptions) will be usedto identify elements. If legends are provided, they are intended merelyas an aid to the reader, and should not in any way be interpreted aslimiting.

In drilling a well, a drill string is used. The drill string cancomprise a drill bit attached to sections of drill pipe. As the well isdrilled, additional sections of drill pipe are added to the drill stringto extend its length until the well is drilled deep enough to reach aformation where substances, such as water, oil or gas, can be extractedfrom the well. Sections of pipe are joined together using threadedconnections on the pipe, often referred to as “pin” and “box”, where thepin of one section of pipe is threaded into the box of an adjoiningsection of pipe. The drill string is rotated to turn the drill bit in awellbore in order to drill the well. When the drill string is removedfrom the wellbore, the sections of pipe are typically removed from thedrill string one or more sections at a time.

To make or break the threaded connection between sections of pipe, apower tong device can be used to do so. Known designs use a motor with atransmission to operate the power tong mechanism which grips and turnsone section of pipe relative to an adjacent section of pipe. As one piperotates with respect to the adjacent section of pipe, the two sectionsof pipe are threaded together or unthreaded so that the two sections ofpipe can be separated from each other.

When “breaking a joint” also know as unthreading the two lengths ofpipe, the power tong uses shifts into a lower gear of the transmissionto increase the torque applied to a first length of pipe being turned toa level required to break the joint. Then, after the joint is broken,the power tong is shifted to a higher gear of the transmission causingan increase in the rotational speed of the first length of pipe beingturned to unthread the first length of pipe from the second length ofpipe and thus break the connection. When a making a joint between thetwo lengths of pipe, the higher gear is first used to start the threadedconnection by rotating a first length of pipe at a relatively highrotational speed. Then, the transmission is shifter into a lower gear toincrease the torque applied to a first length of pipe being turned to alevel required to make the joint so that the first and second lengthsare firmly connected together.

FIG. 1 illustrates a three dimensional, front view of a torque impactmitigator 10, to be used in conjunction with a power tong 12 on an oildrilling rig 14. The torque impact mitigator 10 is anchored to thedrilling rig 14. A cable 16 is connected at one end 16 a to one end 10 aof the torque impact mitigator 10, and on an opposite second end 16 b tothe power tong 12. A second end 10 b of the torque impact mitigator 10can be mounted to a support 13 of an oil well rig. The power tong 12 istypically suspended from the oil drilling rig by a cable 18. The torqueimpact mitigator 10 reduces rotation torque impact of the power tong 12and holds the power tong in position with respect to the pipes ortubulars being connected to each other or disconnected from each other.

Typically, there are several types of pipe or tubulars 17 screwedtogether one piece to another, end to end, until the entire number ofsections of pipe required for the job are joined together and run intothe ground below the rig floor. Even through the pipes 16 being formedinto a casing string are often formed of steel, when they are screwedtogether, care has to be taken, especially when the torque is increasedto ensure a tight connection, to stop the rotation without the powertong tightening too much because of the inertia. When this occurs, thesleeves interconnecting the adjacent sections of pipe can be damaged.

FIG. 2 is a front, three-dimensional view of the torque impact mitigator10. The torque impact mitigator 10 includes a housing assembly 20,comprising a first end cap 22 and second end cap 24, and a hydraulictube or hydraulic cylinder 26 that is secured between the first end cap22 and second end cap 24. A piston rod 28 extends out from the first endcap 22 and is threaded to a rod clevis 30. The first and second end caps22 and 24 are secured to opposite ends of the hydraulic tube or cylinder26 by four tie rods 32 a, 32 b, 32 c, and 32 d to form housing assembly20.

Referring to FIG. 3, each of the four tie rods 32 a, 32 b, 32 c, and 32d extends at a first end through an opening 34 a, 34 b, 34 c, and 34 d,respectively, in the second end cap 24, and at a second opposite endthrough an opening 36 a, 36 b, 36 c, and 36 d, respectively, in thefirst end cap 22. Further, the first end cap 22 has an opening 38through which the piston rod 28 extends. Surrounding the first opening38 and disposed on the underside of the first end cap 22 is a firstcircular slot 40, see FIG. 5, that is designed to receive a first orcompression end 26 a of hydraulic cylinder 26. Similarly, the second endcap 24 has a second circular slot 42 disposed on the underside of thesecond end cap, see FIG. 5, that is designed to receive a second orrebound end 26 b of hydraulic cylinder 26. It must be noted that anysize or shape hydraulic cylinder may be used, depending on theapplication.

The torque impact mitigator 10 contains a piston 44 disposed within thehydraulic cylinder 26 so as to reciprocate back and in the cylinder. Thepiston 44 has one end 28 a of the piston rod secured thereto, typicallyby a threaded connection, within a threaded opening 44 a within thepiston 44. As shown in FIG. 6A, a piston wear ring 48 is fitted into afirst groove 50 formed in the cylindrical surface 44 a of the piston 44.The piston wear ring 48 provides a side load bearing area to preventscoring of the inner surface 27 of the hydraulic cylinder 26. A pistonseal 52 is fitted into a second groove 54 formed in the cylindricalouter surface 44 a of the piston 44. The piston seal 52 can be forexample, an o-ring expander which provides a positive seal with minimalfriction to extend the seal operation under high pressure.

The piston 44 can have a one or more bores 56 extending therethrough.While two bores 56 a and 56 b are illustrated, it is within the scope ofthe invention to use as few as one bore and as many as needed, such asfor example six or eight bores.

Referring to FIG. 4, a compression spring 60 is disposed about thepiston rod 28 and has an outer diameter approximately equal to the innerdiameter of the hydraulic cylinder 26. A plug 62 is disposed within theupper end 60 a of the spring 60. The plug 62, as shown in FIG. 3, has abore 64 extending therethrough to receive piston rod 28. The plug 62 hasan outer cylindrical element 66 which has a diameter that isapproximately equal to the inner diameter of the hydraulic cylinder 26.The outer surface 66 a of the plug 62 rests against the inner surface 22a of the first end cap 22. The plug 62 has an inner cylindrical surfaceelement 62 a which intersects the inner facing surface of the outercylindrical element 66 and has a diameter that is approximately equal tothe inner diameter of the spring 60 so that the inner cylindricalsurface 62 a of the plug 62 can be inserted into a first end 60 a of thespring. An opposite end 60 b of the spring 60 rests against the outersurface 44 a of the piston 44.

One end 28 b of the piston rod 28 is threaded and secured to a threadedopening 68 through the base 70 of a u-shaped rod clevis 72. Holes 74 and75 through the ends of the prongs 76 and 78 of the clevis 72 have aclevis pin 80 extending therethrough. A cross hole 82 receives a splitpin 84 to secure the clevis pin in place. The tang 16 b of a cable 16,as shown in FIG. 1, is held in place by the clevis pin 80.

The second end cap 24 has a u-shaped rod clevis 90 secured thereto.Holes 92 through the ends of the prongs 94 and 96 of the clevis 90 havea clevis pin 98 extending therethrough. A cross hole in the clevis pin98 receives a split pin to secure the clevis pin 98 in place. The tang104 can be mounted to a member 13 a of the oil well member 13 and heldin place by the pin 98.

The hydraulic cylinder 26 has piston member 44 normally biased by spring60 toward the one end of the internal volume of cylinder 26. The piston44 follows the piston rod 57 due to the pushing force of the spring 60.The coil-shaped spring 61 is installed in such a state that it iscompressed between the piston rod 49 and the compression end 22 a ofcylinder 26.

The torque impact mitigator 10 has a hydraulic fluid charged into thehydraulic cylinder 26. The spring 60 is installed to normally bias thepiston 44 against the second end cap 24 and aid in impact mitigation, asshown in FIG. 5. The piston 44 is retained on the end of piston rod 28by a threaded connection. The piston 44 generally subdivides theinternal volume of hydraulic cylinder 26 into a compression volumelocated between piston 44 and the compression end 26 a of cylinder 26,and a rebound volume located between piston 44 and the rebound end 22 bof the cylinder 26.

The movement of the piston 44 toward the compression end 26 a ofcylinder 26, as shown in FIG. 6, results in a reduction in the size ofcompression volume in the compression end of the cylinder, and thesubsequent flow of hydraulic fluid through bores 56 a and 56 b of thepiston 44. The movement of the piston 44 toward the compression end 26 asimultaneously enlarges the rebound volume in the cylinder 26 betweenthe piston 44 and the rebound end 26 b. As piston 44 moves towards thecompression end 26 a of cylinder 26, the spring 60 compresses and slowsthe movement of the piston 44 which in turn slows the movement of therod clevis 72 out of the cylinder. The effect is to mitigate themovement of the device 12, such as a power tong as shown in FIG. 1,secured to the rod clevis 72 causing the piston 44 to pull out of thecylinder 26.

The spring 60 normally biases the piston member 44 towards the reboundend 26 b of the internal volume of cylinder 26, as shown in FIG. 5. Asthe u-shaped rod clevis 72 is moved away from the compression end 26 aof the hydraulic cylinder 26, the spring contracts and developsincreases a greater and greater force on the piston member 44 towardsthe rebound end 22 b of the cylinder 26. The plug 62 limits thecompression of the spring 60 and insures that the spring does not buckleas the spring is compressed.

Once the force pulling the u-shaped rod clevis 72 away from thecompression end 22 a of cylinder 26 is removed, the spring 60 forces thepiston 44 towards the rebound end 22 b of the internal volume ofcylinder 26 and back to an unloaded location at the bottom end 26 b ofthe cylinder 26. As mentioned before, the movement of the piston 44 backto its initial location will be slowed by the flow of hydraulic fluid inthe rebound volume through bores 56 a and 56 b of the piston 44 and intothe compression volume in the compression end of the cylinder 26. Theflow of hydraulic fluid through bores 56 a and 56 b of the piston 44results in the increase of the volume of hydraulic fluid in thecompression volume in the compression end while simultaneouslydecreasing the volume of hydraulic fluid in the rebound volume in therebound end of the cylinder.

The effect of this change in the compression volume of hydraulic fluidin the compression end and while simultaneously decreasing the reboundvolume of hydraulic fluid in the rebound end of the cylinder 26 is tomitigate or slow down the movement of the device, such as a power tong,to prevent damage to the tubular being joined together.

The spring 60 biases the piston member 44 towards the rebound end 22 bof the internal volume of cylinder 26. As the u-shaped rod clevis 72 ismoved away from the compression end 22 a of cylinder 26 of the hydrauliccylinder 26, the spring contracts and increases a greater and greaterforce on the piston member towards the rebound end 22 b of the cylinder26. The plug 62 limits the compression of the spring 62 and insures thatthe spring does not buckle as the spring is compressed. Once the forcepulling the u-shaped rod clevis 72 away from the compression end 22 a ofcylinder 26 is removed, the spring forces the piston 44 towards therebound end 22 b of the internal volume of cylinder 26.

The bores 56 a and 56 b through piston 44 allows the hydraulic fluid tomove between the compression volume located between piston 44 and thecompression end 26 a of cylinder 26, and the rebound volume locatedbetween piston and the rebound end 22 b of the cylinder 26. The size ofthe bores 56 a and 56 b in conjunction with the viscosity of theselected hydraulic fluid controls the speed of the piston as it moves inthe cylinder. The effect of controlling the speed that the piston is tomitigate the movement of the device, i.e. the power tongs, attached tothe compression end of the hydraulic cylinder 26.

FIG. 7 is a front, three-dimensional view of a torque impact mitigator100 which is an alternative embodiment to the torque impact mitigator 10shown in FIG. 2. The torque impact mitigator 100 includes a housingassembly 102, comprising a first end cap 104, a second end cap 106, anda tube or hydraulic cylinder 108 that is secured between the first endcap 104 and second end cap 106. A piston rod 110 extends out from thefirst end cap 104 and is threaded to a rod clevis 112. The first andsecond end caps 104 and 106 are secured to opposite ends of the tube orhydraulic cylinder 108, or any applicable cylinder, by four tie rods 114a, 114 b, 114 c, and 114 d (compare tie rods 32 a-32 d in FIG. 3) toform housing assembly 102.

The torque impact mitigator 100 contains a piston 116 disposed withinthe hydraulic cylinder 108 so as to reciprocate back and in thecylinder. The piston 116 has one end 110 a of the piston rod 110 securedthereto, typically by a threaded connection, within a threaded openingwithin the piston 116. As shown in FIG. 8, a piston wear ring 120 isfitted into a first groove formed in the cylindrical surface 116 a ofthe piston 116. The piston wear ring 120 provides a side load bearingarea to prevent scoring of the inner surface 122 of the hydrauliccylinder 108. A piston seal 124 is fitted into a second groove formed inthe cylindrical outer surface 116 a of the piston 116. The piston seal124 can be for example, an o-ring expander which provides a positiveseal with minimal friction to extend the seal operation under highpressure.

The piston 116 can have a one or more bores 126 a and 126 b extendingtherethrough. While two bores 126 a and 126 b are illustrated, it iswithin the scope of the invention to use as few as one bore and as manyas needed, such as for example six or eight bores.

Referring again to FIG. 8, a compression spring 128 is disposed aboutthe piston rod 110 and has an outer diameter approximately equal to theinner diameter of the hydraulic cylinder 108. A plug 130 is disposedwithin the upper end 128 a of the spring 128. The plug 130 has a bore132 extending therethrough to receive piston rod 110. The plug 130 hasan outer cylindrical element 134 which has a diameter that isapproximately equal to the inner diameter of the hydraulic cylinder 108.The outer surface 130 a of the plug 130 rests against the inner surface104 a of the first end cap 104. The plug 130 has an inner cylindricalsurface element 138 which intersects the inner facing surface of theouter cylindrical element 134 and has a diameter that is approximatelyequal to the inner diameter of the spring 128 so that the innercylindrical surface 138 of the plug 130 can be inserted into a first end128 a of the spring 128. An opposite end 128 b of the spring 128 restsagainst the outer surface 116 a of the piston 116.

One end 110 b of the piston rod 110 is threaded and secured to athreaded opening through the base 140 of a u-shaped rod clevis 142.Holes 144 and 146 through the ends of the prongs 148 and 150 of theclevis 142 have a clevis pin 152 extending therethrough. A cross hole154 receives a split pin 156 to secure the clevis pin in place. The tangof a cable (not shown), compare tang 16 b of cable 16, as shown in FIG.1, is held in place by the clevis pin 152.

The second end cap 158 has a u-shaped rod clevis 160 secured thereto.Holes 162 and 164 through the ends of the prongs 166 and 168,respectively, of the clevis 160 have a clevis pin 170 extendingtherethrough. A cross hole (not shown) in the clevis pin 170 receives asplit pin (not shown) to secure the clevis pin 170 in place.

The hydraulic cylinder 108 has piston member 116 normally biased byspring 128 towards the one end of the internal volume of hydrauliccylinder 108. The piston member 116 follows the piston rod 110 due tothe pushing force of the spring 128. The coil-shaped spring 128 isinstalled in such a state that it is compressed between the piston rod110 and the compression end 108 a of hydraulic cylinder 108.

The torque impact mitigator 100 has a hydraulic fluid charged into thehydraulic cylinder 108. The spring 128 is installed to normally bias thepiston 116 against the second end cap 106 and aid in impact mitigation,as shown in FIG. 8. The piston 116 is retained on the end of piston rod110 by a threaded connection. The piston 116 generally subdivides theinternal volume of hydraulic cylinder 108 into a compression volume 104a located between piston 116 and the compression end 108 a and a reboundvolume 106 a located between piston 116 and the rebound end 108 b. Whilethe hydraulic cylinder 108 is illustrated as a tube, it must be notedthat any size, shape or configuration of hydraulic cylinder may be used,depending on the application.

The movement of the piston 116 toward the compression end 108 a, asshown in FIG. 9, results in a reduction in the size of compressionvolume 104 a of the hydraulic cylinder 108, and the subsequent flow ofhydraulic fluid through bores 126 a and 126 b of the piston 116 fromcompression volume 104 a of the hydraulic cylinder 108 to the reboundvolume 106 a. The movement of the piston 116 toward the compression end108 a simultaneously enlarges the rebound volume 106 a in the hydrauliccylinder 108 between the piston 116 and the rebound end 108 b. As piston116 moves towards the compression end 108 a of hydraulic cylinder 108,the spring 128 compresses and slows the movement of the piston 116 whichin turn slows the movement of the rod clevis 142 out of the hydrauliccylinder 108. The effect is to mitigate the movement of the device 100,such as a power tong as shown in FIG. 1, secured to the rod clevis 142causing the piston 116 to pull out of the hydraulic cylinder 108.

The spring 128 normally biases the piston member 116 towards the reboundend 108 b of the internal volume of hydraulic cylinder 108, as shown inFIG. 9. As the u-shaped rod clevis 142 is moved away from thecompression end 108 a of the hydraulic cylinder 108, the springcontracts and develops a greater and greater force on the piston member116 towards the rebound end 108 b of the hydraulic cylinder 108. Theplug 130 limits the compression of the spring 128 and insures that thespring does not buckle as the spring is compressed.

Once the force pulling the u-shaped rod clevis 142 away from thecompression end 108 a of hydraulic cylinder 108 is removed, the spring128 forces the piston 116 towards the rebound end 108 b of the internalvolume of hydraulic cylinder 108 and back to an unloaded location at therebound end 108 b of the cylinder. As mentioned before, the movement ofthe piston 116 back to its initial location will be slowed by the flowof hydraulic fluid in the rebound volume 106 a through bores 126 a and126 b of the piston and into the compression volume 104 a in thecompression end 108 a of the hydraulic cylinder 108. The flow ofhydraulic fluid through bores 126 a and 126 b of the piston 116 resultsin the increase of the volume of hydraulic fluid in the compressionvolume 104 a in the compression end 108 a while simultaneouslydecreasing the volume of hydraulic fluid in the rebound volume 106 a inthe rebound end 108 b of the hydraulic cylinder 108.

The effect of this change in the compression volume 104 a of hydraulicfluid in the compression end 108 a and while simultaneously decreasingthe rebound volume 106 a of hydraulic fluid in the rebound end 108 b ofthe hydraulic cylinder 108 is to mitigate or slow down the movement ofthe device, such as a power tong, to prevent damage to the tubularsbeing joined together.

The spring 108 biases the piston member 116 towards the rebound end 108b of the internal volume of hydraulic cylinder 108. As the u-shaped rodclevis 142 is moved away from the compression end 108 a of the hydrauliccylinder 108, the spring contracts and increases with a greater andgreater force on the piston member 110 towards the rebound end 108 b ofthe hydraulic cylinder 108. The plug 130 limits the compression of thespring 128 and insures that the spring does not buckle as the spring iscompressed. Once the force pulling the u-shaped rod clevis 142 away fromthe compression end 108 a of hydraulic cylinder 108 is removed, thespring forces the piston 116 towards the rebound end 108 b of theinternal volume of hydraulic cylinder 108.

The bores 126 a and 126 b through piston 116 allows the hydraulic fluidto move between the compression volume 104 a located between piston 116and the compression end 108 a of hydraulic cylinder 108, and the reboundvolume 106 a located between piston and the rebound end 108 b of thehydraulic cylinder 108. The size of the bores 126 a and 126 b inconjunction with the viscosity of the selected hydraulic fluid controlsthe speed of the piston 116 as it moves in the hydraulic cylinder 108.The effect of controlling the speed of the piston 116 is to mitigate themovement of the device, i.e. the power tongs, attached to thecompression end 108 a of the hydraulic cylinder 108.

As illustrated in FIG. 7, a damper tube 200 is provided to furthercontrol the speed of the piston 116 as it moves through the hydrauliccylinder 108, and thereby enhance the mitigation of the movement of thedevice i.e. the power tongs or other devices, attached to thecompression end 108 a of the hydraulic cylinder 108. The damper tube 200connects the compression end 108 a and the rebound end 108 b of thehydraulic cylinder 108. Hydraulic fluid that moves between thecompression volume 104 a located between piston 116 and the compressionend 108 a, and the rebound volume 106 a located between piston and therebound end 108 b flows through the damper tube 200 and can be furthermodulated by an adjustable flow control valve 202. The adjustable flowcontrol valve 202 is located in the damper tube 200 and can be openedand closed to control the flow speed of the hydraulic fluid through thedamper tube. The adjustable flow control valve 202 provides additionalcontrol of the flow speed of the hydraulic fluid through the damper tubeto optimizing system performance, by relying on a flow passage or portwithin the control valve 202 having a variable flow area. Various typesof control valves 202 may be utilized, such as for example but notlimited to gate valves, globe valves, plug valves, and ball valves.

As seen in FIGS. 8 and 9, the damper tube 200 includes an upper end 204and a lower end 206, which are connected to the hydraulic cylinder 108through first and second ports 208 and 210, respectively. Further, asshown in FIG. 8, the upper end 204 and a lower end 206 are connected tothe first and second ports 208 and 210, respectively, thoughelbow-shaped joints 212 and 214, respectively.

The upper port 208 is connected by a passageway 216 to the hydrauliccylinder 208 through a plug port 218, which extends through the outercylindrical element 134 of the plug 130, and the end cap. Therefore,damper tube 200 is in fluid communication with the compression volume104 a, so that hydraulic fluid can flow into and out of the damper tube200 as the piston 116 reciprocates within the hydraulic cylinder.

The lower port 210 is connected by a passageway 220 to the rebound end108 b of the hydraulic cylinder 208 through a port 222, which extendsthrough the end cap 106. Therefore, damper tube 200 is in fluidcommunication with the rebound volume 106 a, so that hydraulic fluid canflow into and out of the damper tube 200 as the piston 116 reciprocateswithin the hydraulic cylinder.

Although the invention has been shown and described with respect to acertain preferred embodiment or embodiments, certain equivalentalterations and modifications will occur to others skilled in the artupon the reading and understanding of this specification and the annexeddrawings. In particular regard to the various functions performed by theabove described components (assemblies, devices, etc.) the terms(including a reference to a “means”) used to describe such componentsare intended to correspond, unless otherwise indicated, to any componentwhich performs the specified function of the described component (i.e.,that is functionally equivalent), even though not structurallyequivalent to the disclosed structure which performs the function in theherein illustrated exemplary embodiments of the invention. In addition,while a particular feature of the invention may have been disclosed withrespect to only one of several embodiments, such feature may be combinedwith one or more features of the other embodiments as may be desired andadvantageous for any given or particular application.

The invention claimed is:
 1. A torque impact mitigator, comprising: ahousing assembly including a hydraulic cylinder having a compression endand a rebound end; a piston disposed within the hydraulic cylinder so asto reciprocate back and forth; a piston rod disposed within thehydraulic cylinder and mounted at a first end to the piston and having asecond end extending out from the compression end; a compression springdisposed between the piston and the compression end of the hydrauliccylinder; a rod clevis secured to the second end of the piston rod tocompress the compression spring into a compressed state when the rodclevis is moved away from the hydraulic cylinder and to release thecompression spring into a relaxed state when the rod clevis is movedtowards the hydraulic cylinder; a plug disposed within an upper end ofthe compression spring and having a bore extending therethrough toreceive the piston rod; and one or more bores disposed through thepiston to allow the passage of hydraulic fluid into the rebound end ofthe hydraulic cylinder when the compression spring is in the compressedstate, and to allow the passage of hydraulic fluid into the compressionend of the hydraulic cylinder when the compression spring is in therelaxed state; and a damper tube connecting the compression end and therebound end of the hydraulic cylinder to direct the hydraulic fluidtherethrough to further control the speed of the piston; wherein a firstend of the torque impact mitigator is configured to be connected to afirst end of a cable, whereby a second end of the cable is configured tobe connected to a power tong; and wherein a second end of the torqueimpact mitigator is configured to be mounted to a support on an oildrilling rig.
 2. The torque impact mitigator of claim 1 wherein thehousing assembly includes first and second end caps, wherein thecompression end of the hydraulic cylinder is secured to the first endcap and the rebound end of the hydraulic cylinder is secured to thesecond end cap.
 3. The torque impact mitigator of claim 1 wherein thecompression spring is disposed about the piston rod and against thepiston and against the plug.
 4. The torque impact mitigator of claim 1wherein the damper tube includes an adjustable flow control valve forfurther modulation of the flow speed of the hydraulic fluid through thedamper tube.
 5. The torque impact mitigator of claim 2 wherein thedamper tube comprises: an upper end and a lower end, which are connectedto the hydraulic cylinder through first and second ports, within thefirst and second end caps, respectively; and the upper end and the lowerend are connected to the first and second ports, respectively, thoughelbow-shaped joints.
 6. The torque impact mitigator of claim 1 whereinthe piston has a piston wear ring fitted into a first groove formedabout a cylindrical outer surface of the piston to provide a side loadbearing area to prevent scoring of an inner surface of the hydrauliccylinder.
 7. The torque impact mitigator of claim 6 wherein a pistonseal is fitted into a second groove formed in the cylindrical outersurface of the piston to provide a positive seal with minimal frictionto extend seal operation under high pressure.
 8. The torque impactmitigator of claim 2 wherein the plug has an outer cylindrical elementwhich has a diameter that is approximately equal to an inner diameter ofthe hydraulic cylinder.
 9. The torque impact mitigator of claim 8wherein an outer surface of the plug rests against an inner surface ofthe first end cap.
 10. The torque impact mitigator of claim 8 whereinthe plug has an inner cylindrical surface element which intersects aninner facing surface of the outer cylindrical element and has a diameterthat is approximately equal to an inner diameter of the compressionspring so that the inner cylindrical surface element of the plug can beinserted into the upper end of the spring.
 11. A torque impact mitigatorto be used in conjunction with a power tong on an oil drilling rig,comprising: the torque impact mitigator is anchored to the drilling rig,whereby a cable is connected at one end to a first end of the torqueimpact mitigator, and on an opposite second end to the power tong; asecond end of the torque impact mitigator is mounted to a support on theoil drilling rig; a housing assembly including a hydraulic cylinderhaving a compression end and a rebound end; a piston disposed within thehydraulic cylinder so as to reciprocate back and forth; a piston roddisposed within the hydraulic cylinder and mounted at a first end to thepiston and having a second end extending out from the compression end; acompression spring disposed between the piston and the compression endof the hydraulic cylinder; a rod clevis secured to the second end of thepiston rod to compress the compression spring into a compressed statewhen the rod clevis is moved away from the hydraulic cylinder and torelease the compression spring into a relaxed state when the rod clevisis moved towards the hydraulic cylinder; a plug disposed within an upperend of the compression spring and having a bore extending therethroughto receive the piston rod; and one or more bores disposed through thepiston to allow the passage of hydraulic fluid into the rebound end ofthe hydraulic cylinder when the compression spring is in the compressedstate, and to allow the passage of hydraulic fluid into the compressionend of the hydraulic cylinder when the compression spring is in therelaxed state; and a damper tube connecting the compression end and therebound end of the hydraulic cylinder to direct the hydraulic fluidtherethrough to further control the speed of the piston.
 12. The torqueimpact mitigator of claim 11 wherein the housing assembly includes firstand second end caps, wherein the compression end of the hydrauliccylinder is secured to the first end cap and the rebound end of thehydraulic cylinder is secured to the second end cap.
 13. The torqueimpact mitigator of claim 12 wherein the compression spring is disposedabout the piston rod and against the piston and against the plug. 14.The torque impact mitigator of claim 13 wherein the damper tube includesan adjustable flow control valve for further modulation of the flowspeed of the hydraulic fluid through the damper tube.
 15. The torqueimpact mitigator of claim 14 wherein the damper tube comprises: an upperend and a lower end, which are connected to the hydraulic cylinderthrough first and second ports, within the first and second end caps,respectively; and the upper end and the lower end are connected to thefirst and second ports, respectively, though elbow-shaped joints. 16.The torque impact mitigator of claim 11 wherein the piston has a pistonwear ring fitted into a first groove formed about a cylindrical outersurface of the piston to provide a side load bearing area to preventscoring of an inner surface of the hydraulic cylinder.
 17. The torqueimpact mitigator of claim 16 wherein a piston seal is fitted into asecond groove formed in the cylindrical outer surface of the piston toprovide a positive seal with minimal friction to extend seal operationunder high pressure.
 18. The torque impact mitigator of claim 12 whereinthe plug has an outer cylindrical element which has a diameter that isapproximately equal to an inner diameter of the hydraulic cylinder. 19.The torque impact mitigator of claim 18 wherein an outer surface of theplug rests against an inner surface of the first end cap.
 20. A methodof using a torque impact mitigator in conjunction with a power tong onan oil drilling rig, comprising: anchoring the torque impact mitigatorto the drilling rig with a cable connected at one end to a first end ofthe torque impact mitigator and on an opposite second end to the powertong; mounting a second end of the torque impact mitigator to a supporton the oil drilling rig; constructing the torque impact mitigator from ahousing assembly including a hydraulic cylinder with a compression endand a rebound end; disposing a piston within the hydraulic cylinder soas to reciprocate back and forth; mounting a piston rod at a first endto the piston and extending a second end of the piston rod out from thecompression end of the hydraulic cylinder; compressing a compressionspring between the piston and the compression end of the hydrauliccylinder into a compressed state when the piston is moved towards thecompression end of the hydraulic cylinder and releasing the compressionspring into a relaxed state when the piston is moved towards the reboundend of the hydraulic cylinder; reducing the buckling of the compressionspring from as the spring is compressed with a plug having a boreextending therethrough disposed within an upper end of the compressionspring; and causing the passage of hydraulic fluid through one or morebores in the piston into the rebound end of the hydraulic cylinder whenthe compression spring is in the compressed state and causing thepassage of hydraulic fluid through the one or more bores in the pistoninto the compression end of the hydraulic cylinder when the compressionspring is in the relaxed state; and further controlling the speed of thepiston by directing hydraulic fluid through a damper tube having anadjustable flow control valve and interconnecting the compression endand the rebound end of the hydraulic cylinder.